Computer access control

In computer security, general access control includes identification, authorization, authentication, access approval, and audit. A more narrow definition of access control would cover only access approval, whereby the system makes a decision to grant or reject an access request from an already authenticated subject, based on what the subject is authorized to access. Authentication and access control are often combined into a single operation, so that access is approved based on successful authentication, or based on an anonymous access token. Authentication methods and tokens include passwords, biometric scans, physical keys, electronic keys and devices, hidden paths, social barriers, and monitoring by humans and automated systems.

Both capability-based and ACL-based models have mechanisms to allow access rights to be granted to all members of a group of subjects (often the group is itself modeled as a subject).

Access control systems provide the essential services of authorization, identification and authentication (I&A), access approval, and accountability where:

Authorization involves the act of defining access-rights for subjects. An authorization policy specifies the operations that subjects are allowed to execute within a system.

Most modern operating systems implement authorization policies as formal sets of permissions that are variations or extensions of three basic types of access:

These rights and permissions are implemented differently in systems based on discretionary access control (DAC) and mandatory access control (MAC).

Identification and Authentication (I&A) is the process of verifying that an identity is bound to the entity that makes an assertion or claim of identity. The I&A process assumes that there was an initial validation of the identity, commonly called identity proofing. Various methods of identity proofing are available, ranging from in-person validation using government issued identification, to anonymous methods that allow the claimant to remain anonymous, but known to the system if they return. The method used for identity proofing and validation should provide an assurance level commensurate with the intended use of the identity within the system. Subsequently, the entity asserts an identity together with an authenticator as a means for validation. The only requirements for the identifier is that it must be unique within its security domain.

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